1. Field of the Invention
The present invention relates to a semiconductor laser diode (hereafter denoted as LD), and a module implementing the LD.
2. Related Background Arts
One type of LDs has been known as a wavelength tunable LD, where the LD includes a chirped-sampled-grating (hereafter denoted as CSG) distributed Bragg reflector (hereafter denoted as DBR) whose reflection spectrum includes a plurality of peaks with a specific period, and a sampled-grating (hereafter denoted as SG) distributed feedback (hereafter denoted as DFB) whose gain spectrum includes a plurality of peaks with another specific period. Such an LD may emit light with a wavelength at which one of the reflection peaks in the CSG-DBR and one of the gain peaks in the SG-DFB coincide.